Troubles setting up the mac (Networking)

There are two issues to deal with.

One is "Troubles setting up the PC (Networking)". I'm no expert in this area, but I suspect you will need to set up sharing for the external volume and the printer, on the PC. It's generally easiest to eliminate all possible barriers to success, mostly to do with security (Firewall off, Guest accounts on, wireless encryption off etc), while you get it working, then add them back in one by one to make sure it all still works. Windows file sharing is a mystery beyond contemplation for me, but the settings are all in there somewhere..

On the Mac side, accessing PCs has got easier with every OS release, but Samba (which is what Macs use to access Windows networks) can still be a bit flakey - mostly the issues are to do with authentication. One thing that can sometimes help is to check Applications > Utilities > Directory Access: Services tab > highlight SMB/CIFS, click Configure and enter MSHOME as your Workgroup (if that's the Workgroup you're using on the PC). Another is instead of using the Finder browser, press Apple+K instead and try to access the shared volume directly:
eg: smb://vaio/music
sometimes using the IP address (if you know it) instead of the network name is more successful
eg: smb://10.0.0.2/music
if you're using user accounts (Samba success with Guest accounts not as great as you might hope, in my experience)
you can enter the as much of the full path too, using the format

Code:

smb://workgroupname;username:password@ipadressorcomputername/sharedvolumename

eg: smb://MSHOME;Me:secret@vaio/music

The printer (God willing) if it's been shared on the PC side should show up in Printer Setup Utility: Add Printer If it doesn't show up in the browser, click More Printers > Windows Printers, choose your Workgroup, pick the PC from the list (it will ask for a valid Windows User Account login name and password - not your Mac username/password - if you haven't opened it up), and then you can see and select the printer.

If that doesn't work you can hold down the Option key when clicking More Printers, and instead of Windows Printers, choose Advanced > Device: Windows Printer via SAMBA and go through the same egregious process as above to try and connect with the printer via its SAMBA url
eg: smb://MSHOME;Me:secret@vaio/hplaser

 

Some info on networking

http://forums.macrumors.com/showthread.php?t=54704

and maybe some insights on iTunes sharing...http://www.macosxhints.com/article.php?story=20070424081346722

 

You only need to disable it long enough to get things working, and if it stops working when you add them back in (one at a time), you know that's the problem and not something else.

More stuff added above, and yes, have a look at the general networking guides